SI3453C-B01-GM Silicon Laboratories Inc, SI3453C-B01-GM Datasheet - Page 24

• Manufacturer Part Number: SI3453C-B01-GM
• Description: IC POE CONTROLLER MIDSPAN 40QFN
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3453C-B01-GM

• Package / Case: 40-QFN
• Controller Type: Power over Ethernet Controller (POE)
• Interface: I²C
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 14mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Maximum Power Dissipation: 1.2 W
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Product: Ethernet Controllers
• Standard Supported: IEEE 802.3at, IEEE 802.3af
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 3 V
• Supply Current (max): 14 mA
• Maximum Operating Temperature: + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 336-1840-5

Si3452/3
6. Operational Notes
6.1. Port Turn On
Ports are normally powered by either putting the Si3452 in the auto mode and allowing the Si3452 to control the
powering sequence, or by putting the Si3452 in the manual mode and issuing a turn-on command.
If the port is turned on by putting it in auto mode, the Si3452/3 will take care of all specified timing, and it will take
care of the two-event classification if the first event result is class 4 and PoE+ mode is enabled. However, if
automatic mode operation is not desired after port turn on, the port should be set to semi-auto or manual mode
once it has powered.
If the port is turned on by putting it in manual mode, the normal sequence is to start with the port in semi auto mode
and interrupt on a classification complete, which indicates that there is a valid PD signature and a classification
result is available. Based on the classification result, the host can make a decision to apply power or not. The IEEE
standard requires that a port be powered within 400 msec of a valid detect complete. It is also desirable to power
the port prior to the start of the next detection pulse, which can occur in as little as 300 msec. Therefore, it is
recommended that ports be powered in under 250 msec from the class complete interrupt when using the manual
mode turn on command.
Using manual mode turn-on, detection is not done prior to port turn on, but classification is always performed just
prior to port turn on. A port that presents an invalid classification signature will not be turned on. 2-event
classification is performed if the first event result is class 4 and the port is enabled for PoE+ mode. The port is not
turned on if the classification result is overload or if PoE+ mode is enabled and the second event result is not class
4. The manual mod classification step does not generate a classification complete flag because it is assumed that
the classification was already done in semi-auto mode, and the host has already made the decision to grant power.
If a port turn-on command is issued in semi-auto or auto mode, the port will power, but this is not desireable
because IEEE-compliant timing is not assured.
6.2. Changing the Interrupt Mask
The INT register and INT pin are always synchronized. However, there can be up to a 5 msec delay between an
event that causes or clears an interrupt and the update of the register and pin.
Thus, if the INT mask register is changed to clear an interrupt or to block an interrupt source, there can be up to a
5 msec delay between the change of the INT mask register and the resultant change in the INT register and INT
pin.
Generally, use of the mask register to clear interrupts is not recommended; it is better to clear an interrupt by
reading the appropriate COR register.
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Rev. 0.42